Low Liquid Content Research Articles

Sintering of Titanium Powder Compacts for Containerless Hot Isostatic Pressing

The liquid-phase sintering of Ti-Si binary alloys using mixed elemental powders has been explored. Sintering at low liquid contents avoids excessive porosity and bulging of compacts, and leads to development of a densified surface. Compacts made in this way can be HIPped without a container to full or near full densities. Exploiting the surface densification phenomenon may enable cost-effective net shape manufacturing of full density titanium components.

Confinement of Ionic Liquid by Networked Polymers Based on Multifunctional Epoxy Resins

Networked polymers confining an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EMImTFSI), were prepared by curing a mixture of bisphenol A diglycidyl ether (BADGE) and tetrafunctional epoxy resins with tetraethylenepentamine (TEPA) in the presence of ionic liquid. It was found that addition of the tetrafunctional epoxy resins was inevitable for better ionic liquid confinement. The ionic liquid confinement, ionic conductivity, mechanical strength, and morphology of the materials strongly depended on the ionic liquid content. At a low ionic liquid content (<40 wt %), the material tightly confined the ionic liquid and showed little ionic conductivity with a high Young’s modulus, while at a high ionic liquid content (>40 wt %), it did not confine the ionic liquid showing higher ionic conductivity with a low Young’s modulus. At a high ionic liquid content (>40 wt %), microphase separation between the ionic liquid and the epoxy networked polymer was observed by scanning electron microscopy (SEM). A transition of the microphase separation from discrete sphere to continuous structure was also observed between 40 wt % and 50 wt % ionic liquid contents. This morphology transition caused a drastic change of the material properties around these ionic liquid contents.

Thermal conductivity of a cubic lattice of spheres with capillary bridges

There have been many attempts to develop expressions for thermal conductivity (λ) as a function of liquid content (θ) in granular media such as powders, gravel and soil. We present a new approach based upon a cubic array of solid spheres, with liquid capillary bridges surrounding the solid–solid contacts. Numerical results agree with analytical solutions for the endpoints. For small filling angles (low liquid contents, such that menisci do not coalesce) and for a fixed conductivity ratio α ≡ λsolid/λliquid = λliquid/λgas, we find a simple relationship λ (θ) = λ (θ = 0) + aθb, where the prefactor and exponent are simple functions of α. The power-law relationship also holds for compressed spheres, if the dry conductivity λ (θ = 0) is adjusted for the new porosity. While the results are not trivially applicable to real granular media, they provide a quantitative explanation for the observed phenomenon in soils of the rapid rise in conductivity caused by the addition of a small volume of liquid.

Microstructural Evolution, Hardness, and Alligatoring in the Mushy State Rolled Cast Al-4.5Cu Alloy and In-Situ Al4.5Cu-5TiB2 Composite

A comparative study has been carried out on the microstructural evolution and hardness of the Al-4.5Cu alloy and in-situ Al-4.5Cu-5TiB2 composite, either water quenched from, or subjected to, rolling at mushy zone temperatures. The cast alloy shows coarse α-Al dendrites, while the composite contains rosette-type grains with TiB2 particles located at the grain boundaries. The plate-shaped specimens, in cast or pre-hot-rolled conditions, have been rolled at temperatures corresponding to 10, 20, or 30 vol pct liquid to thickness reductions in the range of 2.5 to 10 pct. While the alloy could be rolled defect free, the cast composites undergo alligatoring, except when thickness reduction is 5 pct or lower at 30 vol pct liquid. Alligatoring is caused by strain localization and shear failure, and is prevented partially on prior hot rolling, causing homogenization and equiaxed grain formation. Mushy state rolling leads to nearly equiaxed grains having bimodal size distributions. The surfaces with a larger volume fraction of finer grains exhibit higher microhardness than the center. Exposure to mushy zone causes grain growth in the alloy but not in the composite, due to Zener pinning by TiB2 particles. On rolling at low liquid content to a large thickness reduction, the unmelted grains deform and work-harden significantly, causing an increase in hardness.

Conduction through an assembly of spherical particles at low liquid contents

The steady-state conduction of heat through the solid phase of a porous material consisting of an assembly of simple cubic packed uniform spheres at low liquid contents with heat conducted from one sphere to the next through annular liquid lenses around the points of contact, is analysed in terms of Legendre polynomials assuming the liquid bridges to behave as isothermal hemispheres around point sources and sinks. The conductance of a sphere is approximately the same when the surface area of the hemisphere is the same as that of the liquid lens assumed to be an isothermal disc for which numerical results of isotherms are compared with the analytical results.

On the Shear Modulus of Two-Dimensional Liquid Foams: A Theoretical Study of the Effect of Geometrical Disorder

The shear modulus of two-dimensional liquid foams in the dry limit of low liquid content has been studied theoretically. The focus is on the effect of geometrical disorder on the shear modulus (besides the influence of surface tension). Various theoretical predictions are formulated that are all based on the assumptions of isotropic geometrical characteristics, incompressible bubbles, and negligible edge curvature. Three of these predictions are based on a transformation of Princen’s theory that is strictly valid only for regular hexagonal bubbles. Another prediction takes into account variations in bubble areas by considering the foam as consisting of approximately regular hexagonal bubbles with varying areas. Two other predictions are solely based on the characteristics of the bubble edges. The first of these is based on the assumption of affine movement of bubble vertices, while the second accounts for nonaffine deformation by considering the interaction with neighboring edges. The theoretical predictions for the shear modulus are compared with the result from a single foam simulation. For the single simulation considered, all predictions, except that based on affine movement of bubble vertices, are close to the value obtained from this simulation.

Viscoelastic modelling of impacted morsellised bone accurately describes unloading behaviour: An experimental study of stiffness moduli and recoil properties

Morsellised bone impaction grafting is commonly used for revision arthroplasty surgery. Several reports have described the mechanical behaviour of this bone material during impaction and loading. In this study we observed the unloading progress. The loose morsellised bone was modified by particle size, particle size distribution, water and fat content. Bone pellets were constructed using different impaction energies. After impaction, the pellets were loaded statically, after which their swelling was recorded at three unloading levels. We deduced two time-dependent recoil properties, the time resistant number (TRN) and the half total swelling time (HTST), and also one stiffness property, the unloading confined modulus of elasticity (UCME). In impacted morsellised bone, the progress of swelling is visco-elastic. Bone pellets with an even distribution of particle sizes have the most rapid recoil. Those with a high liquid content recoil more slowly, and to a significantly greater extent, than pellets with low liquid content. The recoil of pellets with low liquid content is instantaneous, i.e. unrecordable, and the displacement is significantly less than in other pellet samples.

Electro-Optical Properties of UV Stabilized Sub-Micron Dispersion with Low Liquid Crystal Content

ABSTRACT We study a nematic dispersion formed in a UV-polymerized matrix with a low content of a liquid crystal component. The dispersions contains sub-micrometer liquid crystal droplets obtained in a two-step process: (a) phase separation during a fast cooling process (b) stabilization of droplets size by photo-polymerization caused by a low power UV exposure. The dispersion is homogeneous, highly transparent and shows little light scattering at wavelength 633 nm. We demonstrate that it can be used as an electrically-controlled birefringent slab with a relatively low driving voltage and a short response time. For example, application of the electric field 6 V/µm changes phase retardation by π/4 with the characteristic response time of several milliseconds.

New Rheological Correlations for Guar Foam Fluids

Summary Foams provide a highly attractive alternative to conventional non-Newtonian fluids for various oil and gas applications because of their high viscosity and low liquid content. Foams have a long history of proven performance in well stimulations, drilling, acidizing, cleanout operations, and enhanced oil recovery (EOR). Foam apparent viscosity is used in hydraulic (pressure drop) calculations for various pumping operations. Thus, accurate rheological characterization is very important to predict foam viscosity. In this investigation, rheological experiments are carried out with guar gel and guar foam fluids with a ½-in.-pipe viscometer at 1,000 psi and temperatures ranging from 100 to 200°F. Guar, surfactant, and nitrogen (N2) are used as the gelling agent, foaming agent, and gas phase, respectively. Formulations were prepared and tested at several flow rates for qualities ranging from 0 to 80%. This study has shown that both guar gel and guar foam fluids exhibit behavior analogous to the power-law model fluid. The experimental data are used to develop new rheological correlations to predict power-law fluid-flow parameters and, thus, the apparent viscosity of the foam fluids. These new correlations are functions of temperature, foam quality, shear rate, and fluid concentrations and were compared with various published correlations. The available correlations in the literature have assumed that the foam's flow behavior index is similar to that of the liquid phase. This assumption does not support the basic physics that the increase in viscosity decreases the flow behavior index. Our results show that the previous assumption is invalid and leads to a prediction of extremely low apparent viscosity for foam fluids. In contrast to previous studies, we report high apparent viscosities of high-quality foam fluids.

Effect of the Liquid‐Forming Additive Content on the Kinetics of Abnormal Grain Growth in Alumina

Alumina specimens with various amounts of CaO and SiO2 (1:2 ratio) were prepared, and their abnormal grain growth (AGG) kinetics were investigated. A plot of the area fraction covered by abnormal grains versus log (sintering time) had a sigmoidal shape with an apparent incubation period before the onset of AGG. The overall kinetics of AGG was similar to that of a phase transformation controlled by nucleation and growth. The incubation time and the end point of AGG were strongly dependent on the amount of liquid‐forming additives. Correspondingly, the final microstructure was affected by the liquid content: a large grain size and a high aspect ratio at low liquid content and a small grain size and a low aspect ratio at high liquid content.

Size evolution of the unmelted phase during injection molding of semisolid magnesium alloys

A size of the unmelted phase within injection molded Mg–Al–Zn alloy depends on the solid/liquid ratio and the smallest particles are generated at very low liquid contents. For high liquid fractions the reduction of the solid content is mainly accompanied by a reduction in the number of particles, while their size is only slightly decreased.

The role of adsorption and phase change phenomena in the thermophysical characterization of moist porous materials

Phase change phenomena in moist porous media with low liquid content, the typical condition of a porous body at ambient conditions and far from the contact of liquid water, are controlled by the shape of the adsorption isotherms and by the effective liquid-vapor thermodynamic condition within the pores. Usually, heat and mass transfer models are developed under the assumption of thermal and hygrometric equilibrium. This gives rise to an expression of the evaporation source that is too complex in view of the dynamic identification of thermophysical and transport properties of a porous material. In this study, the hypothesis of hygrometric equilibrium is dropped. The phase change rate is considered proportional to the amount of local nonequilibrium through an appropriate delay coefficient. This approach leads to a simple representation of the process and makes manageable the formulation of a coupled heat and mass transfer inverse problem. A comparison with a first group of experiments performed with an open-pore light insulating material (expanded perlite board) confirms the suitability of the proposed approach. However, the analysis shows that, for this material, phase change occurs not far from the hygrometric equilibrium.

Use of Steam Condensing at Subatmospheric Pressures To Reduce Escherichia coli O157:H7 Numbers on Bovine Hide

This study used a laboratory-scale apparatus to apply subatmospheric steam to bovine hide pieces inoculated with Escherichia coli O157:H7 in maximum recovery diluent (MRD) and in high–liquid content and low–liquid content fecal suspensions (HLC fecal and LLC fecal, respectively). The survival of the organism in fecal clods, which were stored for 24 days in a desiccated state, was assessed. Inoculated fecal clods were also treated with subatmospheric steam. Steam treatment at 80 ± 2°C for 20 s reduced E. coli O157:H7 concentrations on hide inoculated to initial concentrations of approximately 7 log10 CFU/g by 5.46 (MRD inoculum), 4.17 (HLC fecal inoculum), and 5.99 (LLC fecal inoculum) log10 CFU/g. The reductions achieved in samples inoculated with LLC feces were larger than in samples inoculated with HLC feces (P < 0.05). Treatment at 80 ± 2°C for 10 s resulted in significantly smaller reductions (P < 0.05) on hide pieces of 2.54 (MRD), 1.94 (HLC fecal), and 2.15 (LLC fecal) log10 CFU/g. There were no significant differences among the reductions observed in all inoculum types in samples treated for 10 s. E. coli O157:H7 inoculated in fecal clods to 7.78 log10 CFU/g and stored at 4 or 15°C survived for at least 24 days. Steam treatment (20 s) of 3-day-old clods reduced surviving E. coli O157:H7 numbers from 4.20 log10 CFU/g to below the limit of detection of the assay used (1.20 log10 CFU/g). This study shows that steam condensing at or below 80 ± 2°C can reduce E. coli O157:H7 when present on bovine hide, reducing the risk of cross contamination to the carcass during slaughter and dressing.

On the relationship between the composition, morphology and function of leaves

1. It is common practice to express measurements of leaf composition and morphology using dry mass as a basis. Relationships established using those measurements are difficult to interpret because the leaves may have different liquid contents or fractional air space. 2. In a previous theoretical investigation, we showed that the liquid content of leaves was important and the following hypotheses were proposed: (1) the mass of nitrogen per unit mass of liquid is relatively constant within leaves and (2) the surface area to volume ratio of leaves is proportional to leaf liquid content. That investigation also proposed that fractional air spaces were important, because they confer plasticity in construction, with apparently minimal cost in terms of CO2 uptake. In this paper we use a set of comprehensive measurements to address the above hypotheses and to assess whether the fractional air space does vary in a consistent manner. 3. We found that the specific gravity of the non‐gaseous fraction in the leaves we measured was within the range ≈ 0·9–3·0 and increased with the fractional air space in a regular manner. Consequently, the specific gravity varied over a much smaller range (≈ 0·9–1·4). The specific gravity at high liquid contents approached unity but at low liquid contents it was variable. 4. The mass of nitrogen (N) per unit mass of liquid was found to be relatively constant (0·01 ± 0·003, n = 76). 5. The surface area to volume ratio was positively correlated with the liquid content (R2 = 0·87, n = 27). 6. The mass of carbon (C) per unit dry mass was relatively constant (0·49 ± 0·04, n = 76). Because N was a constant fraction of the liquid mass but C was a constant fraction of the dry mass, the N:C ratio was positively correlated with the liquid content (R2 = 0·76, n = 27). 7. A comparison with leaf measurements from several external databases confirm that the relationships described above are widely applicable. 8. It is concluded that the composition and morphology of leaves are linked and that leaf function is a consequence of that linkage. Both the liquids and air spaces are integral to leaf function and need to be considered in analysis of experimental results.

Treatment of gases and dust using “droplet columns”

AbstractThe properties of the air‐water state diagram, representing the liquid holdups according to gas velocities, in a 0.075 m diameter column are restated. After measurement of the interfacial areas and mass‐transfer coefficients, the part of the diagram corresponding to high gas velocities and low liquid contents (10 &lt; UG &lt; 14 m/s and 0.005 &lt; UL &lt; 0.04 m/s) was chosen for the treatment of polluted gas streams. Under these conditions, it was shown that a “droplet column” is very efficient for the treatment of gases polluted by acid vapors (SO2, HCl) and dust (iron oxide, talc, etc.). The cost of energy appeared more favorable than for classical bubble columns.

Granulations with surfactants: effects on pasting

When different types of surfactants were incorporated into binder solutions for the granulation of Sulphanilamide (5% w/w), an anionic surfactant (‘Manoxol OT’) caused paste to be formed at the concentration where other surfactants tested produced normal granules. The effect of surfactants on the formation of pastes was considered essential for investigation. Four water-soluble surface-active agents at the usual level of concentration were incorporated into lactose-based powder blends in order to determine the effect of these agents on the massing in granulation. The presence of these surfactants caused pastes to be produced at lower liquid contents than those normally associated with pasting. The tendency of the effect observed was: anionic > cationic > non-ionic surfactants. Such pasting could not be linked with prolonged massing but with foaming and charges of the surfactant. Antifoaming agents when applied did not affect the properties of the granules and compacts.

Kinetics of grain coarsening during sintering of Co-Cu and Fe-Cu Alloys with low liquid contents

The coarsening of grains immersed in varying amount of liquid matrix is investigated in Fe-Cu and Co-Cu alloys at the liquid phase sintering temperatures. Specimens containing 20, 30, and 50 wt pct Cu have been prepared by compacting and sintering mixtures of fine powders. With 50 wt pct of Cu, spherical grains are dispersed in the liquid matrix. With 20 wt pct of Cu, anhedral grains are in contact with the neighbors across grain boundaries or thin liquid films, and the liquid matrix forms continuous prisms along the three grain contacts. The form of the rate law for grain coarsening at all compositions agrees with predictions of the diffusion controlled Ostwald ripening theories of Lifshitz, Slyozov, Wagner, and others. The coarsening rate also increases with decreasing matrix content. The activation energy for grain coarsening does not vary with specimen composition. Therefore, the rate controlling mechanism for coarsening of the anhedral grains in contact with each other appears to be the solution and reprecipitation of solute atoms by diffusion through the liquid matrix.

The geometry and permittivity of snow at high frequencies

The geometry and porosity of dry snow varies widely depending on the history of conditions. The permittivity of dry snow increases with increasing ice content but is not greatly affected by the shapes of the ice particles. In wet snow the permittivity increases with liquid content and the geometry is very important. However, the liquidlike layer has little effect on permittivity. The permittivity is described using Polder and van Santen’s mixing formulae and approximations of the geometries at high and low liquid contents. It is shown that the common assumption of liquid shells over ice spheres is both physically incorrect and leads to large errors.

An overview of seasonal snow metamorphism

The grains in seasonal snow undergo rapid and radical transformations in size, shape, and cohesion. These grain characteristics affect all of the basic properties of snow. Snow is characterized as either wet or dry depending on the presence of liquid water. Wet snow is markedly different at low and high liquid contents. Dry snow is characterized as either an equilibrium form or a kinetic growth form; that is, it is either well rounded or faceted. Of course, many snow grains display either transitional features between two of these categories or features which arise from other processes. Snow is classified depending on the dominant processes of its metamorphism.

Foamed Acid An Effective Stimulation Fluid

Ford, William G.F., SPE, Halliburton Services Summary Dynamic laboratory testing of foamed acid on limestone cores has established the effectiveness of foamed acid as a stimulation fluid. The effects of foam quality, foam stability, and chemical compatibility on fluid loss and fracture flow capacity were investigated. Recommendations are presented for deriving maximum benefits from a foamed acid treatment. Field results are presented that show the effectiveness of foamed acid in the stimulation of both oil and gas wells. Introduction The use of foam in fracturing treatments has gained widespread acceptance in the past few years. Low liquid content, good fluid loss control, and quick cleanup are just a few reasons why foams are being used. The fluid loss properties of foam as a fracturing fluid and the flow of foam through porous media have been investigated by several authors. The use of foamed acid in fracture acidizing has been reported to give the same benefits as foam in hydraulic fracturing treatments. This paper describes work where fluid loss of foamed acid has been measured directly and the effect of foamed acid on fracture conductivity has been studied. This paper presents laboratory data describing the effects of foam quality, foam stability, chemical compatibility, formation permeability, and pressure differential on. fluid loss and fracture flow capacity with foamed acid on limestone. Apparatus and Test Procedure Fluid Loss Tests The system used to study foamed acid fluid loss is illustrated in Fig. 1. The liquid and gas portions of the foam were maintained at a constant volume by separate control mechanisms. A 1,500-mL volume Ampcoloy floating piston cell was used to hold the acid solution. The driving fluid for this cell was supplied by a positive displacement Jaeco pump. Flow rates were set mechanically on the pump and tested to be 20 mL/min at 1,500 psi. The flow rate of nitrogen at 1,500 psi was measured with an integral orifice meter equipped with a digital readout supplied by Fisher Porter with a No. 2 orifice. The meter was calibrated for various nitrogen flow rates at 1,500 psi through the use of a GCA/Precision Scientific wet test meter. The pressure of the system and nitrogen flow rates were adjusted manually by the use of a back pressure regulator for coarse settings and a needle valve for fine settings. Once pressure and flow rate were stabilized at the start of the test, very little adjustment was needed to maintain the proper pressure and flow rate.The foam generator consists of a 180-mL volume Ampcoloy cell and impeller driven at a speed of 2,200 rpm. This type of foam generator was chosen over the wire screen in a pipe type because of the reactive nature of the test solution. With time, the acid would react with and erode the screen, thus limiting the chances of reproducing a foam with the same texture (bubble size) and consistency from test to test.Foamed acid was generated and allowed to pass through two visual flow cells and out to the waste trap through a high-pressure backpressure regulator. The visual flow cells were used to check the condition of the foamed acid before the fluid loss test began, with uniform small bubbles and no gas pockets conditional to a stable foam. Once this condition was reached, a portion of the foamed acid was allowed to flow into the fluid loss cell while continuing to flow foamed acid through the system to the waste trap. JPT P. 7^